Assessment of the compound muscle action potential amplitude return time between exercises or tests in the repetitive nerve stimulation test for Lambert‐Eaton myasthenic syndrome

2020 ◽  
Vol 62 (6) ◽  
pp. 742-745
Author(s):  
Shin J. Oh
Keyword(s):  
Action Potential ◽  
Nerve Stimulation ◽  
Compound Muscle Action Potential ◽  
Return Time ◽  
Stimulation Test ◽  
Action Potential Amplitude ◽  
Muscle Action ◽  
Repetitive Nerve Stimulation ◽  
Muscle Action Potential ◽  
Myasthenic Syndrome

Congenital Myasthenic Syndrome: Presentation, Electrodiagnosis, and Muscle Biopsy

2004 ◽  
Vol 19 (3) ◽  
pp. 175-182 ◽  
Author(s):  
Christina A. Gurnett ◽  
Judy A. Bodnar ◽  
Jeffrey Neil ◽  
Anne M. Connolly
Keyword(s):  
Action Potential ◽  
Nerve Stimulation ◽  
Compound Muscle Action Potential ◽  
Muscle Action ◽  
Repetitive Nerve Stimulation ◽  
Poor Growth ◽  
Congenital Myasthenic Syndromes ◽  
Feeding Difficulties ◽  
Muscle Action Potential ◽  
Myasthenic Syndromes

We report 10 children with congenital myasthenic syndromes diagnosed by clinical features, electrodiagnostic studies, and response to acetylcholinesterase inhibitors. Age at diagnosis (mean = 4.4 years; range 0.2–10 years) correlated with age fatigue was recognized. Symptoms at presentation included mild gross motor development delay (7/10), speech articulation difficulty (5/10), and respiratory and feeding difficulties resulting in poor growth in 7 of 10 children. None of the five children with possible presynaptic abnormalities had decremental compound muscle action potential responses to 2 Hz repetitive nerve stimulation. Instead, electrodiagnostic studies showed a more than 100% increment of compound muscle action potential amplitude during 50 Hz repetitive nerve stimulation in two children and sustained compound muscle action potential decrement to 2 Hz repetitive nerve stimulation after depletion (10 Hz stimulation for 10 min) in four children. Muscle biopsies ( n = 7) showed mild to severe variation in fiber size. Our experience suggests that many children with congenital myasthenic syndromes might be undiagnosed because of atypical presentation and because additional electrophysiologic studies are required.

scholarly journals Pseudomyopathic Changes in Needle Electromyography in Lambert-Eaton Myasthenic Syndrome

2013 ◽  
Vol 2013 ◽  
pp. 1-2 ◽  
Author(s):  
Teppei Komatsu ◽  
Kota Bokuda ◽  
Toshio Shimizu ◽  
Tetsuo Komori ◽  
Reiji Koide
Keyword(s):  
Nerve Stimulation ◽  
Compound Muscle Action Potential ◽  
The Other ◽  
Motor Unit Potential ◽  
Muscle Action ◽  
Repetitive Nerve Stimulation ◽  
Needle Electromyography ◽  
Muscle Action Potential ◽  
Myasthenic Syndrome ◽  
Myopathic Changes

Lambert-Eaton myasthenic syndrome (LEMS) is a rare presynaptic disorder of the neuromuscular junction in association with cancer and subsequently in cases in which no neoplasm has been detected (O’Neill et al., 1988). The diagnosis of LEMS is based on the combination of fluctuating muscle weakness, diminished or absent reflexes, and a more than 60% increment of compound muscle action potential (CMAP) amplitude after brief exercise or 50 Hz stimulation for 1 s in a repetitive nerve stimulation (RNS) test (Oh et al., 2005). On the other hand, needle electromyography (EMG) findings related to LEMS have not been well described. Here, we report a case of LEMS, which showed apparent myopathic changes in needle EMG findings. Furthermore, we retrospectively examined the needle EMG findings in 8 patients with LEMS. In six of the 8 patients, the EMG findings showed myopathy-like findings. Although the findings of needle EMG indicated myopathic changes at a glance, the motor unit potential (MUP) returned to normal after a sustained strong muscle contraction. We propose the name “pseudomyopathic changes” for this phenomenon.

Congenital Myasthenic Syndrome: Presentation, Electrodiagnosis, and Muscle Biopsy

2004 ◽  
Vol 19 (3) ◽  
pp. 175-182
Author(s):  
Christina A. Gurnett ◽  
Judy A. Bodnar ◽  
Jeffrey Neil ◽  
Anne M. Connolly
Keyword(s):  
Action Potential ◽  
Nerve Stimulation ◽  
Compound Muscle Action Potential ◽  
Muscle Action ◽  
Repetitive Nerve Stimulation ◽  
Poor Growth ◽  
Congenital Myasthenic Syndromes ◽  
Feeding Difficulties ◽  
Muscle Action Potential ◽  
Myasthenic Syndromes

We report 10 children with congenital myasthenic syndromes diagnosed by clinical features, electrodiagnostic studies, and response to acetylcholinesterase inhibitors. Age at diagnosis (mean = 4.4 years; range 0.2–10 years) correlated with age fatigue was recognized. Symptoms at presentation included mild gross motor development delay (7/10), speech articulation difficulty (5/10), and respiratory and feeding difficulties resulting in poor growth in 7 of 10 children. None of the five children with possible presynaptic abnormalities had decremental compound muscle action potential responses to 2 Hz repetitive nerve stimulation. Instead, electrodiagnostic studies showed a more than 100% increment of compound muscle action potential amplitude during 50 Hz repetitive nerve stimulation in two children and sustained compound muscle action potential decrement to 2 Hz repetitive nerve stimulation after depletion (10 Hz stimulation for 10 min) in four children. Muscle biopsies ( n = 7) showed mild to severe variation in fiber size. Our experience suggests that many children with congenital myasthenic syndromes might be undiagnosed because of atypical presentation and because additional electrophysiologic studies are required.

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